The present invention, in some embodiments thereof, relates to anti-angiogenic adenovirus vectors, and therapeutic use thereof, and more particularly, but not exclusively, to clinical protocols for treatment of solid tumors in patients with an Ad5-PPE-1-3X-fas-chimera adenovirus vector.
Angiogenesis is a process of new blood vessel formation by sprouting from pre-existing neighboring vessels. This process is common and major feature of several pathologies. Among these are diseases in which excessive angiogenesis is a part of the pathology and thus is a target of therapy, most significantly, cancer. Angiogenesis occurs in tumors and permits their growth, invasion and metastatic proliferation. In 1971, Folkman proposed that tumor growth and metastases are angiogenesis dependent, and suggested that inhibiting angiogenesis may be a strategy to arrest tumor growth.
There are several molecules involved in angiogenesis, from cell surface molecules to transcription factors to growth factors. Hypoxia is an important environmental factor that leads to neovascularization, inducing release of several pro-angiogenic cytokines, including vascular endothelial growth factors (VEGF) and their receptors, members of the angiopoietin family, basic fibroblast growth factor, and endothelin-1 (ET-1). These factors mediate induction of angiogenesis through control of activation, proliferation and migration of endothelial cells.
Recombinant forms of endogenous inhibitors of angiogenesis have been tested for the treatment of cancer, however the potential pharmacokinetic, biotechnological and economic drawbacks of chronic delivery of these recombinant inhibitors have led scientists to develop other approaches. The development of the anti-VEGF monoclonal antibody bevacizumab has validated anti-angiogenic targeting as a complementary therapeutic modality to chemotherapy. Several small molecule inhibitors, including second-generation multi-targeted tyrosine kinase inhibitors, have also shown promise as antiangiogenic agents for cancer.
The drawbacks of chronic delivery of recombinant inhibitors, antibodies, and small molecules, as well as the limited activity manifested when these drugs are administered as monotherapy have led to the development of anti-angiogenic gene therapies. Gene therapy is an emerging modality for treating inherited and acquired human diseases. However, a number of obstacles have impeded development of successful gene therapy, including duration of expression, induction of the immune response, cytotoxicity of the vectors and tissue specificity.
Two general strategies for anti-cancer gene therapy have proposed: tumor directed or systemic gene therapy. The lack of success in targeting gene therapy products to cancerous cells or their environment by systemic treatments, and the danger of significant anti-drug or anti-vector immunity has caused most therapies to be administered to the tumor itself, despite the advantages of systemic administration. “Adenoviral vaccines”, designed to induce immunity to a recombinant antigen or epitope expressed in the patient's body, have been tried but produce mostly disappointing results. Thus, elaborate, potentially dangerous and costly strategies for eluding pathological host immune responses to systemic and repeated administration of therapeutic recombinant adenoviral vectors have been proposed, including immunosuppression, oral tolerization to vector antigens and genetic modification of the vectors (see Bangari et al, Current Gene Therapy 2006; 6: 215-226).
U.S. Pat. No. 5,747,340 teaches use of a murine endothelial cell-specific promoter which shows selectivity towards angiogenic cells, and therapeutic applications thereof.
International Application WO/2008/132729 discloses a non-replicating adenovirus vector (Ad5, E1 deleted), containing a modified murine pre-proendothelin promoter (PPE-1-3X) and a fas-chimera transgene [Fas and human tumor necrosis factor (TNF) receptor] which has been developed, in which the modified murine promoter (PPE-1-3X), is able to restrict expression of the fas chimera transgene to angiogenic blood vessels, leading to targeted apoptosis of these vessels.
Endothelial-specific gene therapy with the PPE-1-3X promoter does not increase the specificity of viral interactions with the host (e.g. transfection) but restricts the expression of the transgene to those tissues that endogenously recognize the modified promoter—angiogenic endothelial cells. The chimeric receptor can trigger the Fas pathway by binding TNFα, which is less toxic in non-tumoral tissues than using the Fas/Fas ligand mechanism, which is highly expressed in non-tumoral normal tissues such as the liver. Further, TNFα was found to be abundant in the microenvironment of tumors adding to the specificity of the transgene activity in the tumor and its surroundings.
Preliminary studies have shown that a single systemic injection of a PPE-1-3X-fas chimera results in transgene expression restricted to the tumor-bearing organ, causing tumor growth retardation, necrosis of the blood vessels in the metastatic tumor mass and reduction in tumor burden in B16 melanoma and Lewis lung carcinoma mice models.
However, an effective procedure for administration of a therapeutic amount of a recombinant anti-angiogenic adenovirus vector in the clinical setting is still lacking. As such, there is a great need for defining the parameters of clinically viable protocols for anti-angiogenic-adenoviral treatment of conditions associated with neovascularization, such as cancer, without the disadvantages of the current methods as described herein.